connie mariano, who yesterday on cnn called the governor a time bomb. >> i'm a physician more than i am a democrat or republican, and i worry about this man dying in office. >> she must be a genius. >> reporter: the governor questioned how dr. mariano could diagnose him from her office in arizona. >> and it's completely irresponsible. my 12-year-old son comes to me last night and says dad, are you going to die? >> hey! bring it, fat boy! >> chris christie said he's not sure if he's going to run for re-election next year. he was like, oh, i'll collapse that bridge when i get to it. >> reporter: the governor's weight has been a constant issue, which he has handled both with humor -- days ago, eating a donut on the set of his chief tormentor, david letterman -- and with humility. here's what he told diane sawyer about his work with a personal trainer. >> what do you say to yourself to psych yourself into it? >> ah, i just look in the mirror, diane. i just go, okay, i got to get healthier. >> reporter: christie, who was slender and athletic as a young man, insists his health is still good.